1. Field of the Invention
The present invention generally relates to cranes and, more particularly, is concerned with a portable crane.
2. Description of the Prior Art
Cranes have been described in the prior art. However, none of the prior art devices disclose the unique features of the present.
In U.S. Pat. No. 5,348,439, dated Sep. 20, 1994, Kuhn, Jr., disclosed a truck which has been adapted to receive the unloading device of the present invention. The unloading device includes a removable rotatable jib frame which is mounted on the partition walls of the truck. An elongated hollow lever arm member is attached to the jib frame for unloading a load. The lever arm member utilizes a mechanical advantage for unloading a load. It incorporates a braking system together with a chain retraction system for ease in safety of operation.
In U.S. Pat. No. 5,156,517, dated Oct. 20, 1992, Boissonneault disclosed a removable hoist system for a doorway of a van which comprises, when in position, a post vertically mounted in the doorway and an arm having one end secured to the post. The arm during operation extends horizontally from the post and a lift mechanism is secured to the other end of the arm, for lifting or lowering objects with respect to the van. A lower plate is secured to the floor of the van where the post is mounted and an aperture centrally positioned in the plate, and an upper plate is secured to a frame portion of the van in the upper part of the doorway, vertically above the lower plate with an aperture centrally positioned in this upper plate. Pins removably received in the aperture of the plates to hold the post in vertical position during operation outwardly extend from the ends of the post. The post is of a length so that when it is in position with its pins in the apertures there is sufficient clearance at the top to permit lifting of the post so that the lower pin is clear of the aperture for removal of the post. The plates have sufficient load bearing strength when secured in position in the van to withstand a predetermined weight of object when lifted or lowered by the lift mechanism.
In U.S. Pat. No. 3,578,179, filed on Jan. 16, 1969, Fujioka disclosed a support portion which includes depending pins at the upper end thereof for fitting within a hole in a corner casting of an associated structure such as a container or the like. A locking bar and a spaced retainer member are carried at the lower part of the support portion and engage a corner port portion of the associated structure for holding the support portion in place. A load-carrying portion is swingably carried by said support portion, the load-carrying portion including a horizontally extending member having means at the outer end for carrying a load.
In U.S. Pat. No. 1,540,630, dated Jun. 2, 1925, Jenks and Nelson disclosed an invention which relates to hoisting devices, and contemplates a structure primarily intended to facilitate the handling of hogs on a farm when butchering. More specifically stated, the invention contemplates the provision of a device adapted to be pivotally mounted upon the door frame of a barn or the like, and constructed to raise and support a hog suspended therefrom.
In U.S. Pat. No. 5,207,337, dated May 4, 1993, Massey disclosed a portable crane which includes a bracket mounted on a shaft extending upwardly from bearings on the vehicle, a boom extending outwardly from the bracket, a spool rotatable in the bracket carrying a cable, which extends outwardly around a pulley, a hook on the outer end of the cable for supporting a load, and a pair of slack adjusters, one of which receives the shaft for rotating the latter and consequently the boom between use and transport positions, the other slack adjuster engaging the spool for rotating the latter to wind the cable thereon.
In U.S. Pat. No. 4,782,962, dated Nov. 8, 1988, Hackworth, et al., disclosed a portable, backpackable crane lift involving a retractable boom, boom cable, winch and winch cable mounted to a wheeled frame with extendable axles all which fold into a compact unit. A shoulder harness apparatus which attaches to the folded unit for carrying converts to a ballast carrying extension of the frame during operation. Such a lift is readily carried up a ladder for use on flat roofs to raise and place air conditioning heat exchangers and the like.
In U.S. Pat. No. 3,638,806, dated Feb. 1, 1972, Hippach disclosed a portable crane with extendable boom of concentrically and eccentrically disposed telescoping tubes in which the first section is a rigid, high-strength square tube and the remaining sections are of progressively reduced diameters with a large diameter cylindrical tube as a second section defining with the first section triangular channels therebetween at the four corners to house sheaves and cable flights of an extension cable system that provides a mechanical advantage greater than two to one for extending the second section and the remaining telescoped tube sections proportionately.
While these cranes may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described.